Abstract
BackgroundGlycosyltransferases comprise a highly divergent and polyphyletic multigene family that is involved in widespread modification of plant secondary metabolites in a process called glycosylation. According to conserved domains identified in their amino acid sequences, these glycosyltransferases can be classified into a single UDP-glycosyltransferase (UGT) 1 superfamily.ResultsWe performed genome-wide comparative analysis of UGT genes to trace evolutionary history in algae, bryophytes, pteridophytes, and angiosperms; then, we further investigated the expansion mechanisms and function characterization of UGT gene families in Brassica rapa and Brassica oleracea. Using Hidden Markov Model search, we identified 3, 21, 140, 200, 115, 147, and 147 UGTs in Chlamydomonas reinhardtii, Physcomitrella patens, Selaginella moellendorffii, Oryza sativa, Arabidopsis thaliana, B. rapa, and B. oleracea, respectively. Phylogenetic analysis revealed that UGT80 gene family is an ancient gene family, which is shared by all plants and UGT74 gene family is shared by ferns and angiosperms, but the remaining UGT gene families were shared by angiosperms. In dicot lineage, UGTs among three species were classified into three subgroups containing 3, 6, and 12 UGT gene families. Analysis of chromosomal distribution indicates that 98.6 and 71.4% of UGTs were located on B. rapa and B. oleracea pseudo-molecules, respectively. Expansion mechanism analyses uncovered that whole genome duplication event exerted larger influence than tandem duplication on expansion of UGT gene families in B. rapa, and B. oleracea. Analysis of selection forces of UGT orthologous gene pairs in B. rapa, and B. oleracea compared to A. thaliana suggested that orthologous genes in B. rapa, and B. oleracea have undergone negative selection, but there were no significant differences between A. thaliana –B. rapa and A. thaliana –B. oleracea lineages. Our comparisons of expression profiling illustrated that UGTs in B. rapa performed more discrete expression patterns than these in B. oleracea indicating stronger function divergence. Combing with phylogeny and expression analysis, the UGTs in B. rapa and B. oleracea experienced parallel evolution after they diverged from a common ancestor.ConclusionWe first traced the evolutionary history of UGT gene families in plants and revealed its evolutionary and functional characterization of UGTs in B. rapa, and B. oleracea. This study provides novel insights into the evolutionary history and functional divergence of important traits or phenotype-related gene families in plants.
Highlights
Glycosyltransferases comprise a highly divergent and polyphyletic multigene family that is involved in widespread modification of plant secondary metabolites in a process called glycosylation
We have identified 3, 21, 140, 200, 115, 147, and 147 UDP-dependent glycosyltransferases (UGTs) genes in C. reinhardtii, P. patens, S. moellendorffii, O. sativa, A. thaliana, B. rapa, and B. oleracea respectively
After phylogenetic analysis of these UGT genes in the seven plant species, we found that the UGT80 gene family is a common ancient gene family that is shared by algae, bryophytes, pteridophytes, and angiosperms, and the UGT74 gene family is shared by ferns and angiosperms, and the remaining UGT gene families are shared by angiosperms
Summary
Glycosyltransferases comprise a highly divergent and polyphyletic multigene family that is involved in widespread modification of plant secondary metabolites in a process called glycosylation. Glycosylation can occur during the terminal synthesis of many other molecules such as glycoproteins, proteoglycans, and hormones. Acylation, and methylation reactions, glycosylation performs a significant function in the diversity and complexity of plant secondary metabolites. Glycosyl transfer reactions have been highlighted as the most important biotransformation on earth, as in quantitative terms, these reactions account for the assembly and degradation of the bulk of biomass [3]. Glycosylation is believed to perform an important function in plant defense and stress tolerance [4] because aglycones include plant hormones, secondary metabolites involved in stress and defense responses, and xenobiotics, such as herbicides [2]
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